Japan plans to accelerate a warship building program to make two frigates a year to patrol the fringes of the East China Sea, where it disputes island ownership with China, three people with knowledge of the plan said.

Japan previously was building one 5,000-ton class destroyer a year, but will now make two 3,000-ton class ships a year, beginning from the April 2018 fiscal year, the people said, declining to be identified as they are not authorized to talk to the media.

It aims to produce a fleet of eight of the new class of smaller, cheaper vessels, which may also have mine-sweeping and anti-submarine capabilities.